PROJECT ABSTRACT One million adults in the United States receive mechanical ventilation for acute respiratory failure in the intensive care units (ICUs) annually and up to 80% of them develop delirium during their ICU stay. Presence of delirium predisposes older adults to immediate in-hospital complications including a longer length of ICU and hospital stay, increased risk of in-patient mortality and elevated costs of care. In addition, ICU delirium is associated with long-term post-discharge complications such as development of cognitive impairment and dementia. Recent research studies exploring pharmacological strategies to manage ICU delirium have not demonstrated efficacy; a limitation also acknowledged in the Society of Critical Care Medicine 2018 Pain, Agitation/Sedation, Delirium, Immobility, and Sleep Disruption guidelines. Music listening is a non-pharmacological intervention that has shown to decrease over-sedation, anxiety and stress in critically ill patients, factors that could predispose to ICU delirium. We conducted a randomized pilot clinical trial, which showed that slow-tempo relaxing music could improve delirium/coma free days in mechanically ventilated critically ill patients. Our team is now proposing to conduct a large randomized clinical trial called ?Decreasing Delirium through Music (DDM) in Critically Ill Older Adults to evaluate the efficacy of a seven-day slow-tempo music intervention on the primary outcome of delirium/coma free days among mechanically-ventilated older adults admitted to the ICU. The trial has the following aims: 1. Test the efficacy of music intervention in improving delirium/coma free days among mechanically ventilated patients as compared to attention control. 2. Test the efficacy of music intervention in improving delirium severity, pain and anxiety among mechanically ventilated patients as compared to attention control. 3. Test the efficacy of music intervention in improving the long-term neuropsychological outcomes as compared to attention control. Achievement of the aforementioned aims will provide an efficacious and scalable intervention to reduce delirium and improve brain health.